A combination of methods will be used to investigate selected aspects of the molecular architecture of the membranes of enveloped viruses and of the molecular events associated with enveloped virus-cellular plasma membrane interaction. The viruses to be studied are influenza, parainfluenza, and rhabdoviruses. The envelopes of these viruses will be used as biochemically and biologically well-characterized model biological membranes. It is proposed to use a number of experimental techniques including electron microscopy, fluorescence microscopy with an emphasis on spin label electron spin resonance methods in conjunction with biochemical methodology. Specific problems to be investigated include the study of the interactions in the viral envelope between membrane-associated proteins and lipids. The molecular events associated with virus-attachment to cells, virus-induced cell-cell fusion and hemolysis, and virus-entry will be investigated.